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A Method to Test the Efficacy of Handwashing for the Removal of Emerging Infectious Pathogens

Handwashing is widely recommended to prevent infectious disease transmission. However, little comparable evidence exists on the efficacy of handwashing ...

Tufts University

Treating household water with low-cost, widely available commercial bleach is recommended by some organizations to improve water quality and reduce disease in developing countries. I analyzed the chlorine concentration of 32 bleaches from 12 developing countries; the average error between advertised and measured concentration was 35% (range = -45%-100%; standard deviation = 40%). Because of disparities between advertised and actual concentration, the use of commercial bleach for water treatment in developing countries is not recommended without ongoing quality control testing.

Viability of commercially available bleach for water treatment in developing countries.

Almost a billion persons lack access to improved drinking water, and diarrheal diseases cause an estimated 1.87 million deaths per year. Sodium dichloroisocyanurate (NaDCC) tablets are widely recommended for household water treatment to reduce diarrhea. Because NaDCC is directly added to untreated water sources, concerns have been raised about the potential health impact of disinfection by-products. This study investigated trihalomethane (THM) production in water from six sources used for drinking (0.6-888.5 nephelometric turbidity units) near Arusha, Tanzania. No sample collected at 1, 8, and 24 hours after NaDCC addition exceeded the World Health Organization guideline values for either individual or total THMs. Ceramic filtration, sand filtration, cloth filtration, and settling and decanting were not effective mitigation strategies to reduce THM formation. Chlorine residual and THM formation were not significantly different in NaDCC and sodium hypochlorite treatment. Household chlorination of turbid and non-turbid waters did not create THM concentrations that exceeded health risk guidelines.

Disinfection by-product formation and mitigation strategies in point-of-use chlorination with sodium dichloroisocyanurate in Tanzania.

Household water treatment (HWTS) methods, such as boiling or chlorination, have long been recommended in emergencies. While there is increasing evidence of HWTS efficacy in the development context, effectiveness in the acute emergency context has not been rigorously assessed. We investigated HWTS effectiveness in response to four acute emergencies by surveying 1521 targeted households and testing stored water for free chlorine residual and fecal indicators. We defined "effective use" as the percentage of the targeted population with contaminated household water who used the HWTS method to improve stored drinking water microbiological quality to internationally accepted levels. Chlorine-based methods were distributed in all four emergencies and filters in one emergency. Effective use ranged widely, from 0-67.5%, with only one pre-existing chlorine program in Haiti and unpromoted boiling use in Indonesia reaching >20%. More successful programs provided an effective HWTS method, with the necessary supplies and training provided, to households with contaminated water who were familiar with the method before the emergency. HWTS can be effective at reducing the risk of unsafe drinking water in the acute emergency context. Additionally, by focusing on whether interventions actually improve drinking water quality in vulnerable households, "effective use" provides an important program evaluation metric.

Use of household water treatment and safe storage methods in acute emergency response: case study results from Nepal, Indonesia, Kenya, and Haiti.

Dispensers are a source-based water quality intervention with promising uptake results in development contexts. Dispenser programs include a tank of chlorine with a dosing valve that is installed next to a water source, a local Promoter who conducts community education and refills the Dispenser, and chlorine refills. In collaboration with response organizations, we assessed the effectiveness of Dispensers in four emergency situations. In the three initial and four sustained response phase evaluations, 70 Dispenser sites were visited, 2057 household surveys were conducted, and 1676 water samples were analyzed. Across the evaluations, reported Dispenser use ranged from 9 to 97%, confirmed Dispenser use (as measured by free chlorine residual) ranged from 5 to 87%, and effective use (as measured by improvement in household water quality to meet international standards) ranged from 0 to 81%. More effective Dispenser interventions installed Dispensers at point-sources, maintained a high-quality chlorine solution manufacturing and distribution chain, maintained Dispenser hardware, integrated Dispensers projects within larger water programs, remunerated Promoters, had experienced project staff, worked with local partners to implement the project, conducted ongoing monitoring, and had a project sustainability plan. Our results indicate that Dispensers can be, but are not always, an appropriate strategy to reduce the risk of waterborne diseases in emergencies.

Effectiveness of chlorine dispensers in emergencies: case study results from Haiti, Sierra Leone, Democratic Republic of Congo, and Senegal.

Application of silver nanoparticles (nAg) or silver nitrate (AgNO3) has been shown to improve the microbiological efficacy of ceramic water filters used for household water treatment. Silver release, however, can lead to undesirable health effects and reduced filter effectiveness over time. The objectives of this study were to evaluate the contribution of nanoparticle detachment, dissolution, and cation exchange to silver elution, and to estimate silver retention under different influent water chemistries. Dissolved silver (Ag(+)) and nAg release from filter disks painted with 0.03 mg/g casein-coated nAg or AgNO3 were measured as a function of pH (5-9), ionic strength (1-50 mM), and cation species (Na(+), Ca(2+), Mg(2+)). Silver elution was controlled by dissolution as Ag(+) and subsequent cation exchange reactions regardless of the applied silver form. Effluent silver levels fell below the drinking water standard (0.1 mg/L) after flushing with 30-42 pore volumes of pH 7, 10 mM NaNO3 at pH 7. When the influent water was at pH 5, contained divalent cations or 50 mM NaNO3, silver concentrations were 5-10 times above the standard. Our findings support regular filter replacement and indicate that saline, hard, or acidic waters should be avoided to minimize effluent silver concentrations and preserve silver treatment integrity.

Silver Dissolution and Release from Ceramic Water Filters.

Household water treatment with chlorine can improve microbiological quality and reduce diarrhea. Chlorination is typically assessed using free chlorine residual (FCR), with a lower acceptable limit of 0.2 mg/L, however, accurate measurement of FCR is challenging with turbid water. To compare potential measures of adherence to treatment and water quality, we chlorinated recently-collected water in rural Kenyan households and measured total chlorine residual (TCR), FCR, oxidation reduction potential (ORP), and E. coli concentration over 72 h in clay and plastic containers. Results showed that 1) ORP served as a useful proxy for chlorination in plastic containers up to 24 h; 2) most stored water samples disinfected by chlorination remained significantly less contaminated than source water for up to 72 h, even in the absence of FCR; 3) TCR may be a useful proxy indicator of microbiologic water quality because it confirms previous chlorination and is associated with a lower risk of E. coli contamination compared to untreated source water; and 4) chlorination is more effective in plastic than clay containers presumably because of lower chlorine demand in plastic.

Evaluating four measures of water quality in clay pots and plastic safe storage containers in Kenya.

Locally manufactured ceramic water filters are one effective household drinking water treatment technology. During manufacturing, silver nanoparticles or silver nitrate are applied to prevent microbiological growth within the filter and increase bacterial removal efficacy. Currently, there is no recommendation for manufacturers to test silver concentrations of application solutions or filtered water. We identified six commercially available silver test strips, kits, and meters, and evaluated them by: (1) measuring in quintuplicate six samples from 100 to 1,000 mg/L (application range) and six samples from 0.0 to 1.0 mg/L (effluent range) of silver nanoparticles and silver nitrate to determine accuracy and precision; (2) conducting volunteer testing to assess ease-of-use; and (3) comparing costs. We found no method accurately detected silver nanoparticles, and accuracy ranged from 4 to 91% measurement error for silver nitrate samples. Most methods were precise, but only one method could test both application and effluent concentration ranges of silver nitrate. Volunteers considered test strip methods easiest. The cost for 100 tests ranged from 36 to 1,600 USD. We found no currently available method accurately and precisely measured both silver types at reasonable cost and ease-of-use, thus these methods are not recommended to manufacturers. We recommend development of field-appropriate methods that accurately and precisely measure silver nanoparticle and silver nitrate concentrations.

Daniele S. Lantagne

Department of Civil and Environmental Engineering

Tufts University

A Method to Test the Efficacy of Handwashing for the Removal of Emerging Infectious Pathogens

Daniele S. Lantagne

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Civil and Environmental Engineering

Tufts University

A Method to Test the Efficacy of Handwashing for the Removal of Emerging Infectious Pathogens

Department of Civil and Environmental Engineering